One example of a conventional reflector for an electronic flash device is shown in FIG. 12 (see, for example, Patent Document 1). This reflector 1 includes a light source housing portion 3 that houses a light source 2 in an inside portion thereof, and an upper surface portion 4 and lower surface portion 5 that are contiguously formed on both sides in a direction that is perpendicular to a longitudinal direction of the light source housing 3. The light source housing portion 3 includes a cylindrical surface portion that is cylindrical and is formed with a center O of the housed light source 2 as a center of the radius of curvature, with an inner surface of the cylindrical surface portion as a second reflective surface 3a. Respective inner surfaces of the upper surface portion 4 and the lower surface portion 5 are first reflective surfaces 4a and 5a. These first reflective surfaces 4a and 5a are formed so as to be symmetrical in the up-down direction about a center plane L of the upper surface portion 4 and the lower surface portion 5 that form an upper/lower pair.
An imaginary plane 7 including contiguous portions 6, 6 where the light source housing portion 3 of the reflector 1 and the upper and lower surface portions 4 and 5 are contiguous is set so as to be displaced toward the rear surface (i.e., on an opposite side to an opening 8 of the reflector 1) by a distance M from the center O of the light source 2. According to this reflector 1, light N outputted from the light source 2 is emitted to the front from an opening 8 with a light distribution angle α (for example, 45°).
Another example of an electronic flash device is disclosed in Patent Document 2. Patent Document 2 discloses a lamp-integrated front grill that is disposed between headlamps that are disposed on the left and right of the front of a vehicle, the front grill enclosing lamps and thereby making it possible to reduce the number of parts and to reduce the number of assembly and attachment steps.
This lamp-integrated front grill is a lamp-integrated front grill disposed between the headlamps disposed on the left and right of the front of a vehicle, is wide in the left-right direction, and includes reflective concave portions that are open to a front surface at both left and right end portions thereof. The lamp-integrated front grill includes a body whose inner surfaces are reflective surfaces, lenses attached to the body so as to cover a front surface thereof, and light bulbs attached to the concave portions of the body. The body is formed so that at portions aside from the reflective concave portions, the lower portions are wide compared to the upper portions. Lens steps are formed across the entire lenses, and the edges of the openings of the reflective concave portions are positioned so as to not block light directly emitted from the light source portions of the lamps to end portions of the lenses.
Patent Document 1
Japanese Laid-Open Patent Publication No. H05-257194 (see Page 2 and FIG. 5)
Patent Document 2
Japanese Laid-Open Patent Publication No. H01-265401 (see Pages 2 and 3, and FIG. 4)
However, for the reflectors of the electronic flash devices described above, and in particular, for the reflector of Patent Document 1, the size of the opening 8 of the pair of the first reflective surfaces 4a and 5a is wide and the light distribution angle α is not considered, so that to direct the emitted direct light from the opening 8 within a predetermined light distribution angle, the reflector has to be long in the depth direction. This has resulted in the problem that electronic flash devices cannot be made slim or miniaturized. Also, although the light distribution angle can be narrowed using a protector, there is a limit on doing so, and since light is emitted outside the light distribution angle, there is also the problem that the radiation efficiency is poor. In addition, since reflected light cannot be used effectively with conventional reflectors, it has been difficult to reduce the size of the opening while maintaining a predetermined optical performance. Also, although conventional reflectors with small openings do exist, in such cases it is necessary to use a special aspherical lens as the protector and an integrated construction, resulting in the problems of such reflectors having a complex construction and being costly.
The present invention was conceived to solve the above problems with the conventional art and it is an object of the present invention to provide a reflector for an electronic flash device, as well as an electronic flash device that uses the reflector, where the shape of the second reflective surface or the like that reflects light emitted from the light source to the rear is adjusted to emit all or a majority of the reflected light from an opening to the front with a predetermined light distribution angle, so that a slim and/or miniaturized construction can be used while maintaining a predetermined optical performance.